Substrate processing apparatus and method of manufacturing semiconductor device

ABSTRACT

Wafer processing with no dummies is described. A apparatus includes: a boat that hold a product substrates in array at all of positions where substrates can be held; a tubular reactor that houses the boat; a furnace surrounding an upper side and a lateral side of the reactor; a heater provided in the furnace and adapted to heat a side portion of the reactor; a ceiling heater provided in the furnace and adapted to heat a ceiling of the reactor; and a cap heater provided inside the reactor and below the boat; a gas supply mechanism individually supplying a gas to a top side of each of the product substrates.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.16/354,864 filed Mar. 15, 2019, based upon and claims the benefit ofpriority from Japanese Patent Application No. 2018-047873 filed on Mar.15, 2018, and Japanese Patent Application No. 2019-034073 filed on Feb.27, 2019, the entire contents of which are incorporated herein byreference.

BACKGROUND Technical Field

This present disclosure relates to a substrate processing apparatus anda method of manufacturing a semiconductor device.

Related Art

For example, a vertical substrate processing apparatus is used for heattreatment of a substrate (wafer) in a process of manufacturing asemiconductor device (device). In the vertical substrate processingapparatus, a plurality of substrates is arrayed and held in a verticaldirection by a substrate holder, and the substrate holder is carriedinto a process chamber. After that, a process gas is introduced into theprocess chamber in a state where the process chamber is heated, and athin film formation processing is performed for the substrate.

JP 2014-208883 A discloses a technique for forming films conformally ona substrate of high pattern density.

SUMMARY

In such prior art as JP 2014-208883 A, uniformity of a film thicknessbetween a substrate arranged at top or bottom position adjacent topattern dummies and other substrates may be degraded when substrates(wafers) with an extremely large processing surface area are processed.Therefore, there is still room for improvement. Particularly, rapiddegradation in the uniformity of the film thickness at the upper end andthe lower end of substrate region is referred to as reactor-scale(macroscopic) loading effect. In the event of such a loading effect, thenumber of substrates suitable as products might be reduced, andproductivity is decreased.

In one aspect of this present disclosure, a substrate processingapparatus includes: a substrate holder configured to hold plurality ofsubstrates in array at respective positions with predetermined intervalsand used to hold a plurality of product substrates at all the positionswhere the substrates are allocable; a tubular reactor including anopening through which the substrate holder can be carried in and out ata lower side and a ceiling with a flat inner surface and houses thesubstrate holder; a furnace body surrounding an upper side and a lateralside of the tubular reactor; a main heater provided in the furnace bodyand configured to heat the side portion of the tubular reactor; aceiling heater provided in the furnace body and configured to heat theceiling; a lid that closes the opening; a cap heater arranged inside thetubular reactor and also located below the substrate holder andconfigured to perform heating; and a gas supply mechanism configured toindividually supply a gas to a top side of each of the plurality ofproduct substrates held by the substrate holder inside the tubularreactor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a substrate processing apparatusaccording to a first embodiment;

FIG. 2 is a longitudinal cross-sectional view of a heat insulationassembly in the substrate processing apparatus of the first embodiment;

FIG. 3 is a perspective view including a cross section of a tubularreactor in the substrate processing apparatus of the first embodiment;

FIG. 4 is a cross-sectional view of the tubular reactor in the substrateprocessing apparatus of the first embodiment;

FIG. 5 is a bottom view of the tubular reactor in the substrateprocessing apparatus of the first embodiment;

FIG. 6 is a configuration diagram of a controller in the substrateprocessing apparatus of the first embodiment;

FIG. 7 is a diagram illustrating analysis results on radicaldistribution relative to holding positions when product wafers are heldat all of holding positions in a boat of the substrate processingapparatus of the first embodiment and when dummy wafers are held aboveand below product wafers at holding positions in a boat of a substrateprocessing apparatus of a comparative example;

FIG. 8 is a diagram illustrating an analysis result on radicaldistribution inside the tubular reactor when the product wafers are heldat all of holding positions in the boat of the substrate processingapparatus of the first embodiment;

FIG. 9 is a schematic diagram of a substrate processing apparatusaccording to a first modified embodiment; and

FIG. 10 is a diagram illustrating an analysis result on radicaldistribution relative to wafer holding positions when dummy wafers areheld above and below product wafers held at holding positions in theboat of the substrate processing apparatus of the comparative example.

DETAILED DESCRIPTION

Embodiments will be described below with reference to the drawings. Notethat “UP” indicated in the drawings indicates an upper side in avertical direction of an apparatus.

First Embodiment

A substrate processing apparatus and a method of manufacturing asemiconductor device according to a first embodiment will be describedwith reference to FIGS. 1 to 8.

<General Structure of Substrate Processing Apparatus>

As illustrated in FIG. 1, a substrate processing apparatus 1 is formedas a vertical heat treatment apparatus to execute a heat treatmentprocess in manufacture of a semiconductor integrated circuit, andincludes a treatment furnace 2 as a furnace body. The treatment furnace2 includes a heater 3 as a main heater arranged along a verticaldirection in order to heat a cylindrical portion of a tubular reactor 4described later.

The heater 3 has a cylindrical shape and is arranged along the verticaldirection around the cylindrical portion (side portion in the presentembodiment) of the tubular reactor 4 described later. The heater 3includes, in the vertical direction, a plurality of heater unitsobtained by dividing the heater into a plurality of units. In thepresent embodiment, the heater 3 includes an upper heater 3A, a centerupper heater 3B, a center heater 3C, a center lower heater 3D, and alower heater 3E sequentially from an upper side to a lower side. Theheater 3 is installed vertical to an installation floor of the substrateprocessing apparatus 1 by being supported by a heater base (notillustrated) as a holding plate.

The upper heater 3A, center upper heater 3B, center heater 3C, centerlower heater 3D, and lower heater 3E are respectively electricallyconnected to a power regulator 70. The power regulator 70 iselectrically connected to a controller 29. The controller 29 has afunction as a temperature controller to control a power amount to eachof the heaters by the power regulator 70. A temperature in each of theupper heater 3A, center upper heater 3B, center heater 3C, center lowerheater 3D, and lower heater 3E is controlled by controlling a poweramount of the power regulator 70 by the controller 29. The heater 3 alsofunctions as an activation mechanism (excitation unit) to activate(excite) a gas with heat as described later.

The tubular reactor 4 constituting a reaction container (processingcontainer) is arranged on an inner side of the heater 3. The tubularreactor 4 is made of a heat resistant material such as Quartz (SiO₂) orsilicon carbide (SiC), and is formed in a cylindrical shape having anupper end closed and a lower end opened. The tubular reactor 4 has adouble tube structure including an outer tube 4A and an inner tube 4Bjoined to each other at a flange 4C located in a lower end. In otherwords, each of the outer tube 4A and the inner tube 4B is formed in acylindrical shape, and the inner tube 4B is arranged inside the outertube 4A. The outer tube 4A is provided with a ceiling portion 72 havingan upper end closed. Additionally, the inner tube 4B is provided with aceiling 74 having an upper end closed, and the inner tube 4B has a lowerend opened. The ceiling 74 has a flat inner surface. The outer tube 4Ais arranged in a manner surrounding an upper side and a lateral side ofthe inner tube 4B.

The flange 4C is provided at a lower portion of the outer tube 4A. Theflange 4C has an outer diameter larger than an outer diameter of theouter tube 4A, and protrudes outward. An exhaust port 4D communicatingwith the inside of the outer tube 4A is provided near the lower end ofthe tubular reactor 4. The entire tubular reactor 4 including theabove-described components is integrally formed of a single material.The outer tube 4A is formed relatively thick so as to withstand apressure difference when the inside thereof is vacuumed.

The treatment furnace 2 includes, on an upper side of the heater 3, aside heat insulator 76 and an upper heat insulator 78 which are arrangedso as to respectively cover an obliquely upper side and an upper side ofthe ceiling portion 72 of the outer tube 4A. As an example, the sideheat insulator 76 having a cylindrical shape is provided at the upperportion of the heater 3, and the upper heat insulator 78 is fixed to theside heat insulator 76 in a state of being bridged over the side heatinsulator 76. With this structure, the treatment furnace 2 surrounds theupper side and the lateral side of the tubular reactor 4.

A ceiling heater 80 to heat the ceiling portion 72 of the outer tube 4Aof the tubular reactor 4 and the ceiling 74 of the inner tube 4B isprovided on an upper side of the ceiling portion 72 of the outer tube 4Aand also at a lower wall of the upper heat insulator 78. In the presentembodiment, the ceiling heater 80 is provided outside the outer tube 4Aand electrically connected to the power regulator 70.

The controller 29 controls a power amount to the ceiling heater 80 bythe power regulator 70. With this structure, a temperature of theceiling heater 80 is controlled independently from the temperatures ofthe upper heater 3A, center upper heater 3B, center heater 3C, centerlower heater 3D, and lower heater 3E.

A manifold 5 has a cylindrical or a truncated cone shape and made of ametal or Quartz, and is provided so as to support the lower end of thetubular reactor 4. The manifold 5 has an inner diameter larger than aninner diameter of the tubular reactor 4 (inner diameter of the flange4C). With this structure, an annular space described later is formedbetween the lower end (flange 4C) of the tubular reactor 4 and a sealcap 19 described later. This space or a member in the vicinity of thespace will be collectively referred to as a furnace throat.

The inner tube 4B includes, on a side surface thereof, a main exhaustvent 4E at the more back (higher) side of the tubular reactor 4 than theexhaust port 4D, and supply slits 4F located at positions opposite tothe main exhaust vent 4E. Each supply slit 4F is a slit elongating inthe circumferential direction, and a plurality of the supply slits 4F isaligned in the vertical direction at equal intervals and provided in amanner corresponding to the respective wafers 7. The main exhaust vent4E includes slits similar to the supply slits 4F and providescommunication between the inside and the outside of inner tube 4B. Oneor more openings (apertures) that substantially face whole region wherewafers 7 as substrates are arranged may be sufficient for the mainexhaust vent 4E and the supply slits 4F. Such openings may be realizedby a single vertically elongated opening or any other openings witharbitrary shape in arbitrary placement facing directly to each wafers orspaces over the respective wafers without any obstacle. The main exhaustvent 4E and the supply slits 4F may further have an slit-shaped openinglocated corresponding to a confined space under the lowest wafers 7.

The inner tube 4B further includes a plurality of sub-exhaust vents 4Gat positions located on the more inner side of the tubular reactor 4than the exhaust port 4D and also located closer to the opened side thanthe main exhaust vent 4E, and the sub-exhaust vents 4G providecommunication between a process chamber 6 and an exhaust space S(hereinafter, a space between the outer tube 4A and the inner tube 4Bwill be referred to as the exhaust space S). Additionally, a pluralityof bottom exhaust vents 4H and 4J to provide communication between theprocess chamber 6 and a lower end of the exhaust space S is also formedat the flange 4C (see FIG. 5). Furthermore, nozzle introduction holes 4Kare formed at the flange 4C (see FIG. 5). In other words, the lower endof the exhaust space S is closed by the flange 4C except for the bottomexhaust vents 4H and 4J and the like. The sub-exhaust vents 4G and thebottom exhaust vents 4H and 4J function to mainly exhaust an axial purgegas described later.

The exhaust space S between the outer tube 4A and the inner tube 4B isprovided with one or more nozzles 8 to supply a process gas such as asource gas in a manner corresponding to positions of the supply slit 4F.Each nozzle 8 is connected to a gas supply pipe 9 that passes throughthe manifold 5 and supplies the process gas (source gas).

Each gas supply pipe 9 includes a channel on which a mass flowcontroller (MFC) 10 functioning as a flow rate controller and a valve 11functioning as an on-off valve are provided sequentially from anupstream direction. A gas supply pipe 12 to supply an inert gas isconnected to the gas supply pipe 9 on a more downstream side than thevalve 11. The gas supply pipe 12 is provided with an MFC 13 and a valve14 sequentially from the upstream direction. Mainly, the gas supply pipe9, MFC 10, and valve 11 constitute a process gas supply system.

The nozzle 8 is provided inside the gas supply space S1 in a mannerstanding from a low portion of the tubular reactor 4. One or a pluralityof nozzle holes (spouts) 8H to supply a gas is provided on a sidesurface and an upper end of each nozzle 8. Since the plurality of nozzleholes 8H is opened in a manner corresponding to the respective openingsof the supply slits 4F so as to face a center of the tubular reactor 4,the gas can be injected toward the wafers 7 through the inner tube 4B.Gas supply mechanism is a general idea including nozzle 8, nozzlechamber 42, supply slits 4F and also the process gas supply system. Thegas supply mechanism discharges process gases into the process chamber 6from up close to the side of the wafers 7 and delivers the gasesindividually to a top side of all the wafers 7. Supply amount may beadjusted by degree of apertures of the nozzle 8 or supply slit 4F.

An exhaust pipe 15 to exhaust atmosphere contained inside the processchamber 6 is connected to the exhaust port 4D. The exhaust pipe 15 isconnected to a vacuum pump 18 functioning as a vacuum exhaust device viaa pressure sensor 16 functioning as a pressure detector (pressure meter)that detects pressure inside the process chamber 6 and via an autopressure controller (APC) valve 17 functioning as a pressure regulator(pressure adjuster). The APC valve 17 can perform vacuum exhaust andvacuum exhaust suspension inside the process chamber 6 by being openedand closed while the vacuum pump 18 is activated. Furthermore, the APCvalve 17 can adjust a pressure inside the process chamber 6 by adjustinga degree of valve opening on the basis of pressure information detectedby the pressure sensor 16 while the vacuum pump 18 is activated. Mainly,the exhaust pipe 15, APC valve 17, and pressure sensor 16 constitute anexhaust system. The vacuum pump 18 may also be included in the exhaustsystem.

A seal cap 19 functioning as a lid that can airtightly close an opening90 at a lower end of the manifold 5 is provided below the manifold 5.That is, the seal cap 19 functions as the lid to close the outer tube 4Aof the tubular reactor 4. The seal cap 19 is made of, for example, ametal such as stainless steel or a nickel-based alloy, and is formed ina disk shape. The seal cap 19 has an upper surface provided with anO-ring 19A as a seal member abutting on the lower end of the manifold 5.

Additionally, the seal cap 19 has the upper surface on which a coverplate 20 to protect the seal cap 19 is installed for a portion locatedon a more inner side than a lower-end inner circumference of themanifold 5. The cover plate 20 is made of a heat-resistant andcorrosion-resistant material such as quartz, sapphire or SiC, and isformed in a disk shape. Since the cover plate 20 is not required to havemechanical strength, the cover plate 20 can be formed with a smallthickness. The cover plate 20 is not limited to a component preparedseparately from the seal cap 19 but may also be a thin film or thinlayer of nitride or the like with which an inner surface of the seal cap19 is coated or by which quality of the inner surface is modified. Thecover plate 20 may also include a wall upstanding from a circumferentialedge along an inner surface of the manifold 5.

A boat 21 functioning as a substrate holder is housed inside the innertube 4B of the tubular reactor 4. The boat 21 made of a heat-resistantmaterial such as quartz or SiC and includes a plurality of upstandingsupport columns 21A and a disk-shaped boat top plate 21B that fixesupper ends of the plurality of support columns 21A to each other.Additionally, the boat 21 includes an annular bottom plate 86 that fixeslower ends of the plurality of support columns 21A to each other (seeFIG. 2). Here, the boat top plate 21B is an example of a top plate. Inthe present embodiment, note that the boat 21 includes the annularbottom plate 86 at the lower ends of the plurality of support columns21A, but a disk-shaped bottom plate may be provided instead of thebottom plate 86.

For example, the boat 21 supports, in a horizontal attitude, 25 to 200pieces of wafers 7 in multiple stages vertically arrayed with centers ofthe wafers mutually aligned. The wafers 7 are arrayed at regularintervals in the boat. In the present embodiment, all of the wafers 7held in the boat 21 are product wafers on which integrated circuitpatterns are formed. In other words, in the boat 21, a plurality ofproduct wafers each having a indented surface is held at all ofpositions where the wafers 7 can be held. In this context, productwafers may include one or more monitor wafers or fill-dummy wafers thatalso have integrated circuit patterns or effective surface area as largeas the product wafers. Assuming that the number of positions where thewafers 7 can be held is integral multiplication of the number of wafers(such as 25 pieces) that can be housed in a wafer container such as afront opening unified pod (FOUP), efficiency of substrate processingincluding transfer from the wafer container to the boat 21 can bemaximized. For example, a product wafer has, on a front side, a patternhaving a predetermined specific surface area of more than 50 times asubstrate on which no pattern is formed (dummy wafer).

The inner tube 4B of the tubular reactor 4 may desirably has a minimuminner diameter so as to be able to safely carry in and out the boat 21.In the present embodiment, a diameter of the boat top plate 21B is setto 90% or more and 98% or less of the inner diameter of the inner tube4B, or a pitch between adjacent wafers 7 held by the boat 21 is set to 6mm or more and 16 mm or less, for example. Moreover, the diameter of theboat top plate 21B is preferably 90% or more and 98% or less, morepreferably 92% or more and 97% or less, and still more preferably 94% ormore and 96% or less of the inner diameter of the inner tube 4B. Thediameter of the boat top plate 21B less than 90% of the inner diameterof the inner tube 4B causes gas transport by diffusion (especiallyinflow of the excessive SiCl₂ from upper side of the boat top plate intolower side), and so the redundant gas becomes more influential forenvirons. On the other hand, the diameter of top plate 21B greater than98% of the inner diameter of the tube 4B may not comply with a certainsafety factor against collisions between the boat 12 and the tube 4B.The top plate 21B can suppress the diffusion more by its diameter of notless than 92% and still more by the diameter of not less than 94% of theinner diameter of inner tube 4B. The top plate 21B can improve thesafety factor more by its diameter of not greater than 97% and stillmore by the diameter of not greater than 96% of the inner diameter ofinner tube 4B Additionally, the pitch between adjacent wafers 7 ispreferably 6 mm or more and 16 mm or less, more preferably 7 mm or moreand 14 mm or less, and still more preferably 8 mm or more and 12 mm orless. The pitch set to less than 6 mm makes the gas difficult to flowsmoothly between the adjacent wafers 7, and then uniformity of filmwithin an wafer may be degraded. Moreover, the pitch less than 16 mmdecreases productivity while improvement of the uniformity is limited.The pitch of 7 mm or more contributes better uniformity and the pitch of8 mm or more contributes still better uniformity. The pitch of 14 mm orless provides better productivity and the pitch of 12 mm or lessprovides still better productivity.

Additionally, in the present embodiment, volume of an upper end spacepartitioned from others by the boat top plate 21B and interposed betweenthe ceiling 74 and the boat top plate 21B is set to, for example, 1 timeor more and 3 times or less volume of a space interposed between thewafers 7 adjacent (neighboring) to each other and held by the boat 21.Here, the volume of the upper end space interposed between the ceiling74 and the boat top plate 21B is preferably 1 time or more and 3 timesor less, more preferably 1 time or more and 2.5 times or less, and stillmore preferably 1 time or more and 2 times or less the volume of thespace interposed between the wafers 7 adjacent to each other. That is,it is preferable that the volume of the upper end space interposedbetween the ceiling 74 and the boat top plate 21B is as small aspossible. However, it is required that the gas flows smoothly to themain exhaust vent 4E. Since the volume of the upper end space interposedbetween the ceiling 74 and the boat top plate 21B is set to 3 times orless the volume of the space interposed between the wafers 7 adjacent toeach other and held by the boat 21, an absolute amount of the excess gasis reduced. Furthermore, since the volume of the upper end spaceinterposed between the ceiling 74 and the boat top plate 21B is set to 1time or more the volume of the space interposed between the wafers 7adjacent to each other and held by the boat 21, the gas flows smoothlyto the main exhaust vent 4E.

main exhaust vent 4E has one or more openings (apertures) facing edgesof wafers 7 or upper spaces of the wafers (i.e. spaces interposedbetween two wafers 7 adjacent to each other and held by the boat 21 anda space between the top plate 21 and an wafer 7 at the top position ofthe boat 21) and exhaust the atmosphere inside the process chamber 6.Hence a gas flux (cross flow) is formed in which the gas flows along andparallel to whole top surface of the wafers 7 in the tubular reactor 4from gas supply mechanism (supply slits 4F) to main exhaust vent 4Ewhile mass transport across the wafers (in vertical direction) is almostlimited to diffusion though a gap between the wafers 7 and the innertube 4B.

A heat insulation assembly (heat insulation structure) 22 describedlater is provided at a lower portion of the boat 21. The heat insulationassembly 22 has a structure in which conduction or transmission of heatin the vertical direction becomes small, and normally has a cavityinside thereof. The assembly 22 has a height (vertical length) biggerthan a diameter of the wafers. The inside of the assembly 22 can bepurged by the axial purge gas. In the tubular reactor 4, an upperportion where the boat 21 is arranged will be referred to as aprocessing region A of the wafer 7, and a lower portion where the heatinsulation assembly 22 is arranged will be referred to as a heatinsulation region B.

A rotation mechanism 23 to rotate the boat 21 is installed on a side ofthe seal cap 19 opposite to the process chamber 6. The rotationmechanism 23 is connected to a gas supply pipe 24 of the axial purgegas. The gas supply pipe 24 is provided with an MFC 25 and a valve 26sequentially from the upstream direction. One purpose of this purge gasis to protect the inside of the rotation mechanism 23 (e.g., bearing)from a corrosive gas and the like used in the process chamber 6. Thepurge gas is supplied from the rotation mechanism 23 along the rotaryshaft 66 and guided into the heat insulation assembly 22.

A boat elevator 27 is provided in the vertical direction below andoutside the tubular reactor 4, and operates as an elevation mechanism(transfer mechanism) that moves up and down the seal cap 19. With thisstructure, the boat 21 and the wafers 7 supported by the seal cap 19 arecarried in and out of the process chamber 6. Meanwhile, while the sealcap 19 is moved down to a lowermost position, a shutter (notillustrated) closing a lower end opening of the tubular reactor 4 can beprovided instead of the seal cap 19.

A temperature sensor (temperature detector) 28 functioning as aprocessing space temperature sensor to detect a temperature inside thetubular reactor 4 is installed inside an outer wall of a side portion ofthe outer tube 4A or on an inner side of the inner tube 4B. Thetemperature sensor 28 includes, for example, a plurality ofthermocouples arrayed in the vertical direction. Although notillustrated, the temperature sensor 28 is electrically connected to thecontroller 29. The controller 29 adjusts respective power amounts to theupper heater 3A, center upper heater 3B, center heater 3C, center lowerheater 3D, and lower heater 3E with the power regulator 70, on the basisof temperature information detected by the temperature sensor 28, andthereby the temperature inside the process chamber 6 is made to havedesired temperature distribution.

Additionally, a temperature sensor (temperature detector) 82 functioningas an upper end space temperature sensor to detect a temperature of anupper portion inside the tubular reactor 4 is installed on an outer wallof the ceiling portion 72 of the outer tube 4A. The temperature sensor82 includes, for example, a plurality of thermocouples arrayed in ahorizontal direction. Although not illustrated, the temperature sensor82 is electrically connected to the controller 29. The controller 29adjusting a power amount to the ceiling heater 80 with the powerregulator 70, on the basis of temperature information detected by thetemperature sensor 82, and thereby the temperature of the upper portioninside the process chamber 6 is made to have desired temperaturedistribution.

The controller 29 is a computer to control the entire substrateprocessing apparatus 1, and electrically connected to the MFCs 10 and13, the valves 11 and 14, the pressure sensor 16, the APC valve 17, thevacuum pump 18, the rotation mechanism 23, the boat elevator 27, and thelike to receive signals from these components and control thesecomponents.

FIG. 2 illustrates a cross-sectional view of the heat insulationassembly 22 and the rotation mechanism 23. As illustrated in FIG. 2, therotation mechanism 23 includes a casing (body) 23A formed in asubstantially cylindrical shape having an upper end opened and a lowerend closed, and the casing 23A is fixed to a lower surface of the sealcap 19 with a bolt. Inside the casing 23A, a cylindrical inner shaft 23Band an outer shaft 23C formed in a cylindrical shape having a diameterlarger than a diameter of the inner shaft 23B are coaxially providedsequentially from the inner side. Additionally, the outer shaft 23C isrotatably supported by a pair of upper and lower inner bearings 23D and23E interposed in a space with the inner shaft 23B and a pair of upperand lower outer bearings 23F and 23G interposed in a space with thecasing 23A. On the other hand, the inner shaft 23B is fixed to thecasing 23A and is not rotatable.

Magnetic fluid seals 23H and 23I to separate vacuum from the air of anatmospheric pressure are installed on the inner bearing 23D and theouter bearing 23F, that is, on the process chamber 6 side. A worm wheelor a pulley 23K to be driven by an electric motor (not illustrated) orthe like is mounted on the outer shaft 23C.

A sub-heater support column 33 functioning as an auxiliary heatingmechanism to heat the wafers 7 from the lower side inside the processchamber 6 is vertically inserted through the inside of the inner shaft23B. The sub-heater support column 33 is a pipe made of quartz, andconcentrically holds the cap heater 34 at an upper end of the sub-heatersupport column. The sub-heater support column 33 is supported by asupport portion 23N made of a heat resistant resin at an upper endposition of the inner shaft 23B. Additionally, at a lower portion of thesub-heater support column 33, a space between the sub-heater supportcolumn 33 and the inner shaft 23B is airtightly sealed with vacuumfitting 23P.

The cap heater 34 is electrically connected to the power regulator 70(see FIG. 1). The controller 29 controls the power amount to the capheater 34 by the power regulator 70 (see FIG. 1). Consequently, atemperature of the cap heater 34 is controlled independently fromtemperatures of the upper heater 3A, center upper heater 3B, centerheater 3C, center lower heater 3D, lower heater 3E, and ceiling heater80.

A cylindrical rotary shaft 36 having a lower end provided with a flangeis fixed to an upper surface of the outer shaft 23C formed in a flangeshape. The sub-heater support column 33 passes through a cavity of therotary shaft 36. In an upper end portion of the rotary shaft 36, adisk-shaped rotary table 37 is fixed while keeping an interval h1 fromthe cover plate 20, and a penetration hole where the sub-heater supportcolumn 33 passes through is formed at a center of the rotary table 37.

On an upper surface of the rotary table 37, a heat insulator holder 38to hold a heat insulator 40 and a cylindrical portion 39 areconcentrically placed and fixed with screws or the like. The cylindricalportion 39 includes a top plate 39A as a disk-shaped upper surface toclose an upper end portion. The top plate 39A is arranged on the lowerside of the boat 21 and constitutes a bottom of the processing region A(see FIG. 1). Additionally, the annular bottom plate 86 that fixes alower end portion of the boat 21 is fitted to the top plate 39A in thecircumference of the top plate 39A. The heat insulation assembly 22includes the rotary table 37, heat insulator holder 38, cylindricalportion 39, and heat insulator 40, and the rotary table 37 constitutes abottom plate (cradle). A plurality of exhaust holes 37A each having adiameter (width) h2 is formed on the rotary table 37 near an edgethereof in a rotationally symmetric manner.

In the present embodiment, volume of a lower end space interposedbetween the bottom plate 86 or the top plate 39A on the upper surface ofthe heat insulator 40 and a wafer 7 held at a lowermost position in theboat 21 where the wafer can be held is set to 0.5 times or more and 1.5times or less the volume of a space interposed between the wafers 7adjacent to each other and held in the boat 21. Here, the volume of thelower end space interposed between the wafer 7 and the bottom plate 86or the top plate 39A is preferably 0.5 times or more and 1.5 times orless, more preferably 0.6 times or more and 1.3 times or less, and stillmore preferably 0.7 times or more and 1.0 times or less the volume ofthe space interposed between the wafers 7 adjacent to each other. If thevolume of the lower end space is set to greater than 1.5 times thevolume of the interposed space between the adjacent wafers 7, anincreased absolute amount of the excess gas arises a bigger influence inthe event that the excess gas leaks. If the volume of the lower endspace is set to less than 0.5 times, ease of gas displacement among thelower end space is diminished. The lower end space of 0.6 times or morepermits gases to flow more smoothly toward the nearest main exhaust vent4E. The lower end space of 0.7 times or more permits gases to flow stillmore smoothly. Furthermore, the lower end space of 1.3 times or less thevolume of the interposed space between the adjacent wafers 7, enable toreduce more excess gas and the lower end space of 1 time or less enableto reduce still more.

In the cap heater 34, a temperature sensor 84 functioning as a lower endspace temperature sensor to detect a temperature of the cap heater 34 ora temperature of a lowermost wafer 7 is installed. The temperaturesensor 84 includes, for example, a plurality of thermocouples arrayed inthe horizontal direction at a height same as a height of the cap heater34. Although not illustrated, the temperature sensor 84 is electricallyconnected to the controller 29 (see FIG. 1). The controller 29 adjusts apower amount supplied to the cap heater 34 with the power regulator 70(see FIG. 1), on the basis of temperature information detected by thetemperature sensor 84, and thereby a temperature at a lower portioninside the process chamber 6 is made to have desired temperaturedistribution.

The controller 29 adjusts, by the power regulator 70, power (i.e., poweramount) supplied to the upper heater 3A, center upper heater 3B, centerheater 3C, center lower heater 3D, lower heater 3E, ceiling heater 80,and cap heater 34 on the basis of the temperatures respectively detectedby the temperature sensor 82 in the upper end space, temperature sensor28 in the processing space, and temperature sensor 84 in the lower endspace such that temperatures of the plurality of wafers 7 held at all ofthe positions are equalized. In other words, the temperatures in theentire processing region A can be equalized

The heat insulator holder 38 has a cylindrical shape including, at acenter thereof, a cavity where the sub-heater support column 33 passesthrough. A lower end of the heat insulator holder 38 includes a leg 38Chaving an outward flange shape having an outer diameter smaller than anouter diameter of the rotary table 37. On the other hand, an upper endof the heat insulator holder 38 is opened so as to allow the sub-heatersupport column 33 to protrude therefrom and constitutes a supply port38B of a purge gas.

A channel having an annular cross section is formed between the heatinsulator holder 38 and the sub-heater support column 33 to supply theaxial purge gas to an upper portion of the heat insulation assembly 22.The purge gas supplied from the supply port 38B flows downward in thespace between the heat insulator holder 38 and the inner wall of thecylindrical portion 39 and is exhausted from the exhaust holes 37A tothe outside of the cylindrical portion 39. The axial purge gas exhaustedfrom the exhaust holes 37A flows radially through a clearance betweenthe rotary table 37 and the cover plate 20 and is released to thefurnace throat to purge the furnace throat.

A plurality of reflection plates 40A and a plurality of heat insulatingplates 40B are coaxially installed as the heat insulator 40 at a columnof the heat insulator holder 38.

The cylindrical portion 39 has an outer diameter such that a gap h6between the cylindrical portion 39 and the inner tube 4B has apredetermined value. The gap h6 is desirably set narrow in order tosuppress passage of the process gas and the axial purge gas, and ispreferably set to, for example, from 7.5 mm to 15 mm.

FIG. 3 illustrates a perspective view of the tubular reactor 4 takenalong horizontally. Note that the flange 4C is omitted in FIG. 3. Asillustrated in FIG. 3, the supply slits 4F to supply the process gasinto the process chamber 6 are arrayed in a lattice shape at the innertube 4B, and the supply slits 4F as many as the number of wafers 7(refer to FIG. 1) are formed in a vertical direction and three supplyslits 4F are formed in the lateral direction. Partition plates 41extending in the vertical direction are provided between each of thesupply slits 4F or at both ends thereof arrayed in the lateral directionso as to partition the exhaust space S between the outer tube 4A and theinner tube 4B. Each of the sections separated from the main exhaustspace S by the plurality of partition plates 41 forms a nozzle chamber(nozzle buffer) 42. As a result, the exhaust space S is formed to have aC-shape cross section. An opening directly connecting each of the nozzlechambers 42 to the inside of the inner tube 4B is the supply slits 4Falone. Note that an upper end of each of the nozzle chambers 42 may beclosed at a height substantially same as a height of the upper end ofthe inner tube 4B.

The partition plates 41 are connected to the inner tube 4B but notconnected to the outer tube 4A and a small clearance can be providedtherebetween in order to avoid stress caused by a temperature differencebetween the outer tube 4A and the inner tube 4B. Each of the nozzlechambers 42 is not necessarily completely separated from the exhaustspace S, and may have an opening or a clearance communicating with theexhaust space S, particularly, at the upper end and a lower end thereof.Each of the nozzle chambers 42 is not limited to the one having an outercircumference side partitioned by the outer tube 4A, and a partitionplate formed along the inner surface of the outer tube 4A may also beseparately provided.

In the inner tube 4B, three sub-exhaust vents 4G are provided atpositions opened to a side surface of the heat insulation assembly 22.One of the sub-exhaust vents 4G is provided in a direction same as thatof the exhaust port 4D, and at least a part of the opening is arrangedat a height overlapping with a pipe of the exhaust port 4D.Additionally, other two sub-exhaust vents 4G are arranged near both sideportions of the nozzle chamber 42. Alternatively, the three sub-exhaustvents 4G may be arranged at positions spaced apart from each other at a180-degree interval on the circumference of the inner tube 4B.

As illustrated in FIG. 4, nozzles 8 a to 8 c are installed in the threenozzle chambers 42, respectively. Side surfaces of the nozzles 8 a to 8d are provided with nozzle holes 8H respectively in a manner openedtoward the center of the tubular reactor 4. A gas ejected from each ofthe nozzle holes 8H is intended to flow from the supply slits 4F intothe inner tube 4B, but a part of the gas does not flow directly. Sinceeach of the nozzles 8 a to 8 c is installed in an independent spaceprovided by the partition plates 41, it is possible to suppress mixtureof the process gases supplied from the respective nozzles 8 a to 8 cinside the nozzle chambers 42. Furthermore, a gas staying in each of thenozzle chambers 42 can be discharged to the exhaust space S from theupper end or the lower end in each of the nozzle chambers 42. With thisstructure, it is possible to suppress formation of a thin film orgeneration of a by-product due to mixture of process gases inside thenozzle chamber 42. Note that, alone in FIG. 4, a purge nozzle 8 d thatcan be optionally installed along the axial direction (verticaldirection) of the tubular reactor is provided in the exhaust space Sadjacent to the nozzle chambers 42. In the following, the descriptionwill be provided assuming that the purge nozzle 8 d is not provided.

FIG. 5 illustrates a bottom view of the tubular reactor 4. Asillustrated in FIG. 5, the flange 4C is provided with the bottom exhaustvents 4H and 4J and the nozzle introduction holes 4K as openings toconnect the exhaust space S (see FIG. 4) to a lower side the flange. Thebottom exhaust vent 4H is an elongated hole provided at a positionclosest to the exhaust port 4D, and the bottom exhaust vents 4J aresmall holes provided at six places along the C-shaped exhaust space S.The nozzles 8 a to 8 c (see FIG. 4) are inserted from the openings ofthe nozzle introduction holes 4K. In a case where the openings of thebottom exhaust vents 4J are too large as described later, a flowvelocity of the axial purge gas passing the respective openings isdecreased, and the source gas or the like enters the furnace throat fromthe exhaust space S due to diffusion. Therefore, the exhaust ports maybe formed as holes each having a central portion with a reduced diameter(narrowed).

As illustrated in FIG. 6, the controller 29 is electrically connected toeach of the MFCs 10, 13, and 25, valves 11, 14, and 26, pressure sensor16, APC valve 17, vacuum pump 18, rotation mechanism 23, boat elevator27, and the like, and automatically controls these components.Additionally, the controller 29 is electrically connected to each of theheater 3 (upper heater 3A, center upper heater 3B, center heater 3C,center lower heater 3D, and lower heater 3E), ceiling heater 80, capheater 34, temperature sensor 28, temperature sensor 82, temperaturesensor 84, and the like, and automatically controls these components.Although not illustrated, the controller 29 is electrically connected tothe heater 3 (upper heater 3A, center upper heater 3B, center heater 3C,center lower heater 3D, and lower heater 3E), ceiling heater 80, and capheater 34 via the power regulator 70.

The controller 29 is formed as a computer including a central processingunit (CPU) 212, a random access memory (RAM) 214, a memory device 216,and an I/O port 218. The RAM 214, memory device 216, and I/O port 218can exchange data with the CPU 212 via an internal bus 220. The I/O port218 is connected to each of the above-described components. Aninput/output device 222 such as a touch panel is connected to thecontroller 29.

The memory device 216 includes, for example, a flash memory, a hard diskdrive (HDD), and the like. The memory device 216 stores, in a readablemanner, a control program to control operation of the substrateprocessing apparatus 1, and programs (recipes such as a process recipeand a cleaning recipe) to cause the respective components of thesubstrate processing apparatus 1 to perform film formation processingand the like in accordance with processing conditions. The RAM 214 isformed as a memory region (work region) in which a program, data, andthe like read by the CPU 212 are temporarily stored.

The CPU 212 reads a control program from the memory device 216 andexecutes the same, also reads a recipe from the memory device 216 inresponse to an input of an operational command or the like from theinput/output device 222, and controls each of the components inaccordance with the recipe.

The controller 29 can be constituted by installing, in a computer, theabove-described program persistently stored in an external memory device(for example, a semiconductor memory such as a USB memory or a memorycard, an optical disk such as a CD or a DVD, or an HDD) 224. The memorydevice 216 and the external memory device 224 are formed ascomputer-readable tangible media. In the following, these memory devicesare collectively and simply referred to as recording media. Note that aprogram may be provided in a computer by using a communication unit suchas the Internet or a dedicated line without using the external memorydevice 224.

<Method of Manufacturing Semiconductor Device>

Next, an exemplary sequence of processing to form a film on a wafer 7(hereinafter also referred to as film formation processing) will bedescribed as a process in manufacturing processes for a semiconductordevice (device) by using the substrate processing apparatus 1 describedabove.

Here, a description will be provided for an example of forming a siliconnitride (SiN) film on each of the wafers 7 by providing, for example,two or more nozzles 8, and supplying a hexa-chloro-disilane (Si₂Cl₆,that is, abbreviated as HCDS) gas as a first process gas (source gas)from a nozzle 8 a and supplying an ammonia (NH₃) gas as a second processgas (source gas) from a nozzle 8 b, respectively. The second process gas(source gas) may also be referred to as a reactant gas. In the followingdescription, note that operation of each of the components of thesubstrate processing apparatus 1 is controlled by the controller 29.

In the film formation processing of the present embodiment, a process ofsupplying the HCDS gas to wafers 7 located inside the process chamber 6,a process of removing the HCDS gas (residual gas) from the inside of theprocess chamber 6, a process of supplying the NH₃ gas to the wafers 7located inside the process chamber 6, and a process of removing the NH₃gas (residual gas) from the inside of the process chamber 6 are repeatedpredetermined number of times (once or more) to form a SiN film on eachof the wafers 7. In the present specification, this film formationsequence will be expressed as follows for the sake of convenience.(HCDS→NH₃)×n=>SiN

In the present embodiment, film formation progresses while SiCl₂ (activespecies) provides Si into a crystal. There are various kinds of routesincluding (1) and (2) shown below in chemical reaction in which SiCl₂ isgenerated from HCDS, and there is not little possibility of the route(2) from an empirical viewpoint.

(1) Dissociative adsorption (chemisorption) of Si₂Cl₆

(2) Adsorption of SiCl₂ that has been decomposed under a predeterminedequilibrium condition of Si₂Cl₆<=>SiCl₂+SiCl₄ in a vapor phase.

In either case, a concentration (partial pressure) of a precursor ofSiCl₂ is decreased near a surface of each wafer 7 due to massconsumption of SiCl₂.

(Wafer Charge and Boat Load)

In the boat 21, a plurality of product wafers each having a patternformed is held at all of positions where the wafers 7 can be held. Whenthe plurality of wafers 7 is charged (wafer charge) in the boat 21, theboat 21 is carried into the process chamber 6 by the boat elevator 27(boat load). At this point, the seal cap 19 is brought into a state inwhich the lower end of the manifold 5 is airtightly closed (sealed) viathe O-ring 19A. A small amount of the purge gas can be supplied into thecylindrical portion 39 by opening the valve 26 from a standby statebefore the wafer charge.

(Pressure Adjustment)

Vacuum exhaust (evacuation) is performed by the vacuum pump 18 such thatthe inside of the process chamber 6, namely, a space where wafers 7exist is made to have a predetermined pressure (vacuum degree). At thispoint, the pressure inside the process chamber 6 is measured by apressure sensor 16, and the APC valve 17 is subjected to feedbackcontrol on the basis of the measured pressure information. Supply of thepurge gas into the cylindrical portion 39 and actuation of the vacuumpump 18 are kept on at least until the processing for the wafers 7 iscompleted.

(Elevated Temperature)

After oxygen and the like are sufficiently exhausted from the inside ofthe process chamber 6, the temperature inside the process chamber 6 isstarted to be elevated. The power amount to the heater 3 (the upperheater 3A, center upper heater 3B, center heater 3C, center lower heater3D, and lower heater 3E) is subjected to feedback control on the basisof temperature information detected by the temperature sensor 28 suchthat the process chamber 6 achieves preferable predetermined temperaturedistribution for film formation. Additionally, the power amount to theceiling heater 80 is subjected to feedback control on the basis oftemperature information detected by the temperature sensor 82.Furthermore, the power amount to the cap heater 34 is subjected tofeedback control on the basis of temperature information detected by thetemperature sensor 84. Heating the inside of the process chamber 6 bythe heater 3 (the upper heater 3A, center upper heater 3B, center heater3C, center lower heater 3D, and lower heater 3E), by the ceiling heater80, and by the cap heater 34 is performed at least until the processingfor the wafers 7 (film formation) is completed. A power applicationperiod to the cap heater 34 does not need to coincide with a heatingperiod by the heater 3. It is preferable that the temperature of the capheater 34 reaches a temperature same as a film formation temperature andan inner surface temperature of the manifold 5 desirably reaches 180° C.or more (for example, 260° C.) immediately before start of filmformation.

Additionally, rotation of the boat 21 and wafers 7 by the rotationmechanism 23 is started. Since the boat 21 is rotated by the rotationmechanism 23 via the rotary shaft 66, rotary table 37, and cylindricalportion 39, the wafers 7 are rotated without rotating the cap heater 34.Consequently, uneven heating can be reduced. The boat 21 and wafers 7are continuously rotated by the rotation mechanism 23 at least until theprocessing for the wafers 7 is completed.

(Film Formation)

When the temperature inside the process chamber 6 is stabilized at apreset processing temperature, steps 1 to 4 are repeatedly executed.Note that the valve 26 may be opened to increase supply of the purge gas(N₂) before starting step 1.

[Step 1: Source Gas Supply Process]

In step 1, the HCDS gas is supplied to wafers 7 inside the processchamber 6. The valve 14 is opened simultaneously with opening of thevalve 11, and the HCDS gas is made to flow into the gas supply pipe 9,and a N₂ gas is made to flow into the gas supply pipe 12. Flow rates ofthe HCDS gas and N₂ gas are adjusted by the MFCs 10 and 13,respectively, and are supplied into the process chamber 6 via the nozzlechambers 42 and then exhausted from the exhaust pipe 15. Since the HCDSgas is supplied to the wafers 7, a silicon (Si)-containing film having athickness that is less than monolayer and up to several atomic layers isformed as a first layer on an outermost surface of each of the wafers 7.

[Step 2: Source Gas Exhaust Process]

After the first layer is formed, the valve 11 is closed and supply ofHCDS gas is stopped. At this point, vacuum exhaust is performed by thevacuum pump 18 inside the process chamber 6 with the APC valve 17 keptopened, and the HCDS gas remaining inside the process chamber 6 and nothaving reacted or having contributed to formation of the first layer isexhausted from the inside of the process chamber 6. Additionally, thesupplied N₂ gas purges the gas supply pipe 9, the inside of the tubularreactor 4, and the furnace throat with the valve 14 and valve 26 keptopened.

[Step 3: Reactant Gas Supply Process]

In step 3, the NH₃ gas is supplied to the wafers 7 inside the processchamber 6. Opening and closing control of the valves 11 and 14 areperformed by a procedure similar to opening and closing control of thevalves 11 and 14 in step 1. The flow rates of the NH₃ gas and N₂ gas areadjusted by the MFCs 10 and 13, respectively, and are supplied into theprocess chamber 6 via the nozzle chambers 42 and then exhausted from theexhaust pipe 15. The NH₃ gas supplied to the wafers 7 reacts with atleast a part of the first layer, that is, the Si-containing film formedon each of the wafers 7 in step 1. With this reaction, the first layeris nitrided and changed (modified) into a second layer containing Si andN, namely, a silicon nitride layer (SiN layer).

[Step 4: Reactant Gas Exhaust Process]

After the second layer is formed, the valve 11 is closed and supply ofthe NH₃ gas is stopped. Then, the NH₃ gas and a reaction by-product,which remain inside the process chamber 6 and have not reacted or havecontributed to formation of the second layer, are exhausted from theinside of the process chamber 6 by processing procedures similar to step1.

A SiN film having predetermined composition and a predetermined filmthickness can be formed on each of the wafers 7 by performing, thepredetermined number of times (n times), a cycle of the above-describedfour steps non-simultaneously, that is, without overlapping.

Examples of processing conditions of the above sequence are as follows:

processing temperature (wafer temperature): 250 to 700° C.;

processing pressure (pressure in process chamber): 1 to 4000 Pa;

HCDS gas supply flow rate: 1 to 2000 sccm;

NH₃ gas supply flow rate: 100 to 10000 sccm;

N₂ gas supply flow rate (nozzle): 100 to 10000 sccm; and

N₂ gas supply flow rate (rotary shaft): 100 to 500 sccm.

The film formation processing can be made to appropriately proceed bysetting the respective processing conditions to values within therespective ranges.

A heat decomposable gas such as the HODS gas may tend to form aby-product film on a surface of a metal rather than on quartz. SiO,SiON, and the like easily adhere to the surface exposed to HCDS (andammonia) gas especially at 260° C. or less.

(Purge and Restoration of Atmospheric Pressure)

After completion of the film formation processing, the valve 14 isopened to supply the N₂ gas into the process chamber 6 from the gassupply pipe 12 and exhaust the gas from the exhaust pipe 15.Consequently, an atmosphere inside the process chamber 6 is replacedwith an inert gas (inert gas replacement), and a remaining sourcematerial and a by-product are removed (purged) from the process chamber6. After that, the APC valve 17 is closed, and the N₂ gas is chargeduntil the pressure inside the process chamber 6 reaches an ordinarypressure (restoration of atmospheric pressure).

(Boat Unload and Wafer Discharge)

The seal cap 19 is moved down by the boat elevator 27 and the lower endof the manifold 5 is opened. Then, the processed wafers 7 are carriedout to the outside of the tubular reactor 4 from the lower end of themanifold 5 in a state that the processed wafers 7 are supported by theboat 21. The processed wafers 7 are extracted from the boat 21.

With execution of the above film formation processing, a SiN filmcontaining nitrogen and the like deposit on a surface of a member insidethe tubular reactor 4 that has been heated, for example, an inner wallof the outer tube 4A, a surface of the nozzle 8 a, a surface of theinner tube 4B, a surface of the boat 21, and the like. Accordingly,cleaning is performed when an amount of such deposits, that is, acumulative film thickness reaches a predetermined amount (thickness)before the deposits are peeled off or fall down. The cleaning processingis performed by, for example, supplying a F₂ gas as a fluorine-based gasinto the tubular reactor 4.

<Actions and Effects>

In the above-described substrate processing apparatus 1 temperatures inthe vertical direction of the process chamber 6 can be controlledsubstantially uniform by controlling the temperatures of the upperheater 3A, center upper heater 3B, center heater 3C, center lower heater3D, lower heater 3E, cap heater 34, and ceiling heater 80, respectively.Therefore, product wafers can be held at all of positions in the boat 21where the wafers 7 can be held, and a dummy wafer can be eliminated.

Additionally, when the source gas decomposed in the gas phase issupplied from the gas supply pipe 9 in a state where the product wafersare held at all of the positions in the boat 21 where the wafers 7 canbe held, a partial pressure of one species (SiCl₂) of a product gasgenerated by the decomposition is made substantially uniform at all ofthe positions in the boat 21 where the wafers 7 are held. Consequently,thicknesses of films formed on the plurality of product wafers arrayedin the vertical direction of the boat 21 can be suppressed from beingnon-uniform among the product wafers.

Furthermore, in the substrate processing apparatus 1, the number ofproduct wafers can be increased and productivity can be improved by, forexample, eliminating dummy wafers arranged on an upper end side and alower end side of the product wafers. Alternatively, instead ofincreasing the number of product wafers, a pitch of the product waferscan be increased by an amount of eliminating the dummy wafers.

Additionally, in the substrate processing apparatus 1, the diameter ofthe boat top plate 21B is set to, for example, 90% or more and 98% orless of the inner diameter of the inner tube 4B, or a pitch betweenadjacent wafers 7 held by the boat 21 is set to, for example, 6 mm ormore and 16 mm or less. Since the diameter of the boat top plate 21B isset to be 90% or more of the inner diameter of the inner tube 4B, gasmovement caused by diffusion (particularly, excessive flow of SiCl₂ fromabove the boat top plate 21B toward the side of the wafers 7) can besuppressed. Furthermore, since the diameter of the boat top plate 21B isset to 98% or less of the inner diameter of the inner tube 4B, the boat21 can be safely carried in and out from the inner tube 4B.

Additionally, the volume of the upper end space interposed between theceiling 74 and the boat top plate 21B is set to, for example, 1 time ormore and 3 times or less the volume of the space interposed between thewafers 7 adjacent (neighboring) to each other and held by the boat 21.Since the volume of the upper end space interposed between the ceiling74 and the boat top plate 21B is set to 3 times or less the volume ofthe space interposed between the wafers 7 adjacent to each other andheld by the boat 21, an absolute amount of the excess gas is reduced.Furthermore, since the volume of the upper end space interposed betweenthe ceiling 74 and the boat top plate 21B is set to 1 time or more thevolume of the space interposed between the wafers 7 adjacent to eachother and held by the boat 21, the gas flows smoothly to the mainexhaust vent 4E.

Additionally, in the substrate processing apparatus the volume of thelower end space interposed between the bottom plate 86 or the top plate39A of the upper surface of the heat insulator 40 and a wafer 7 held atthe lowermost position in the boat 21 where the wafer 7 can be held isset to, for example, 0.5 times or more and 1.5 times or less the volumeof the space interposed between the wafers 7 adjacent to each other andheld by the boat 21. Since the volume of the lower end space interposedbetween the bottom plate 86 or the top plate 39A and the mentioned wafer7 is set to 1.5 times or less the volume of the space interposed betweenthe wafers 7 adjacent to each other, an absolute amount of an excess gasis reduced. Furthermore, since the volume of the lower end spaceinterposed between the bottom plate 86 or the top plate 39A and thementioned wafer 7 is set to 1 time or more the volume of the spaceinterposed between the wafers 7 adjacent to each other, the gas flowsinto the main exhaust vent 4E smoothly.

FIG. 7 illustrates, for the substrate processing apparatus 1 of thefirst embodiment, an analysis result of radical distribution relative toholding positions when pattern wafers (product wafers) are held at allof the holding positions in the boat 21. Additionally, FIG. 10illustrates an analysis result of radical distribution relative to waferholding positions when dummy wafers are held on an upper end side and alower end side of pattern wafers held at the holding positions in theboat 21 of a substrate processing apparatus of a comparative example(see FIG. 7). Here, radicals are atoms or molecules having unpairedelectrons generated when HCDS reacts.

As illustrated in FIG. 10, in the substrate processing apparatus of thecomparative example, a few pieces of dummy wafers not used as productsare held on the upper end side and the lower end side of the patternwafers (product wafers). In the substrate processing apparatus of thecomparative example, a heater arranged along the vertical direction isprovided around a tubular reactor, but temperature sensors 82 and 84like the first embodiment are not provided, and there is no structure inwhich a soaking region is not increased by independently controllingtemperatures of a cap heater and a ceiling heater. Here, since a patternis formed on a pattern wafer, the pattern wafer has large surface areathan surface area of a wafer having no pattern, and radical consumptionis intense promotional to the surface area. In a dummy wafer, no patternis formed (surface area is smaller than the surface area of a patternwafer), and radical consumption is almost none. In the substrateprocessing apparatus of the comparative example, a reason why the dummywafers are arranged on the upper end side and the lower end side of thepattern wafers is to deem the pattern wafers interposed between thedummy wafers as a part of the pattern wafers regularly arrayed in aninfinite length (the part of the pattern wafers is not affected by anedge effect and temperatures and gas concentrations are equalized).

As illustrated in FIG. 10, in the substrate processing apparatus of thecomparative example, it can be grasped that uniformity of radicaldistribution is deteriorated at an upper end portion and lower endportion of the pattern wafers. The reason is that a loading effect iscaused by a difference between the dummy wafers having almost no radicalconsumption and the pattern wafers having intense radical consumption(proportional to each surface area). That is, a radical concentration inthe gas phase is low because the surface area on each of the patternwafers is large and radical consumption is intense, whereas radicalconcentration in the gas phase is high on each of the dummy wafersbecause consumption is little. In a region where the pattern wafer andthe dummy wafer between which there is such an extreme concentrationdifference are adjacent to each other, concentration diffusion occurs inthe gas phase, and the radical concentration difference is reduced.Therefore, the concentration inevitably becomes high in the upper endportion and the lower end portions of the pattern wafers (film thicknessbecomes thick), and uniformity of the film thickness is deteriorated.

On the other hand, in the substrate processing apparatus 1 of the firstembodiment, the pattern wafers (product wafers) are held at all of theholding positions for the wafers 7 in the boat 21. Additionally, in thesubstrate processing apparatus 1, the dummy wafers can be eliminatedbecause temperatures in regions of the upper end portion and the lowerend portion of the pattern wafers can be controlled to be substantiallyuniform by controlling the respective temperatures of the upper heater3A, center upper heater 3B, center heater 3C, center lower heater 3D,lower heater 3E, cap heater 34, and ceiling heater 80.

As illustrated in FIG. 7, it can be grasped that uniformity of radicaldistribution is improved overall when the pattern wafers (productwafers) are held at all of the holding positions for the wafers 7 in theboat 21 (see a broken line in the graph of FIG. 7). The reason is thatthere is no consumption difference between the dummy wafers and thepattern wafers unlike the comparative example because the pattern wafersare held at all of the holding positions for the wafers 7 in the boat21.

However, in FIG. 7, a region of high concentration is still observed inthe upper end portion and the lower end portion of the pattern wafers(product wafers). It is considered that the difference is due to theinfluence of the space outside the pattern wafer region, namely, thespace between the boat top plate 21B and the inner tube 4B of thetubular reactor 4. This space is surrounded by Quartz constituting theinner tube 4B, and radicals are diffused to the vicinity of the wafers 7due to diffusion although there is no active gas flow. Additionally,provided that consumption of radicals on a Quartz surface is equivalentto consumption on a bare wafer (wafer having a surface where a siliconflat surface alone is exposed), a concentration in this space is alsothicker than the concentration on the pattern wafers, and aconcentration difference is caused here.

FIG. 8 illustrates an analysis result on radical distribution relativeto holding positions of the wafers 7 arranged in the vertical directionof the boat 21 at the time of holding pattern wafers (product wafers) atall of the holding positions for the wafers 7 in the boat 21. Asillustrated in FIG. 8, it can be grasped that there is a space having ahigh radical concentration on the upper end side of the boat 21. Toimprove such a situation, substrate processing apparatuses according toa First Modified Embodiment and a Second Modified Embodiment will bedescribed below.

First Modified Embodiment

A substrate processing apparatus 100 according to a First ModifiedEmbodiment will be described with reference to FIG. 9. Note thatcomponents same as those in a first embodiment described above will bedenoted by the same reference signs, and descriptions thereof will beomitted.

As illustrated in FIG. 9, the substrate processing apparatus 100 isprovided with a supply device 101 as a purge gas supply mechanism tosupply a purge gas (inert gas) to an upper end space between a boat topplate 21B and a ceiling 74 of an inner tube 4B. The supply device 101includes: a supply pipe 102 to supply a purge gas; and a nozzle 104provided at an end of the supply pipe 102 and introducing the purge gasinto the upper end space between the boat top plate 21B and the ceiling74 of the inner tube 4B. The nozzle 104 is provided at an upper end sideportion of the inner tube 4B. The supply pipe 102 is provided with anMFC 106 and a valve 108. As the purge gas, N₂ is used, for example.

In the substrate processing apparatus 100, the purge gas is suppliedfrom the supply pipe 102 to the upper end space between the boat topplate 21B and the ceiling 74 of the inner tube 4B via the nozzle 104.Consequently, one species of a product gas (e.g., SiCl₂) is diluted bythe purge gas, and a partial pressure is reduced. That is, a radicalconcentration in the vertical direction of the boat 21 is madesubstantially uniform by diluting a radical concentration in the upperend space between the boat top plate 21B and the ceiling 74 of the innertube 4B with the purge gas. Therefore, it is possible to moreeffectively suppress thicknesses of films formed on wafers 7 from beingnon-uniform among the wafers 7 at the time of holding product wafers atall of positions in a boat 21 where the wafers 7 can be held.

Note that a N₂ gas added with H₂ may also be used as a purge gas in thesupply device 101. Since hydrogen bonds with SiCl₂ and consumes theSiCl₂, it can be expected that an equilibrium condition is shifted in adirection of decreasing a SiCl₂ concentration. Alternatively, thesubstrate processing apparatus 100 may have a structure provided with asupply pipe and a nozzle, instead of the supply device 101, to supply,via a manifold 5, an inert gas to the upper end space between the boattop plate 21B and the ceiling 74 of the inner tube 4B from a gas supplypipe 12 that supplies the inert gas.

Second Modified Embodiment

Next, a substrate processing apparatus according to a Second ModifiedEmbodiment will be described. Note that components same as those of afirst embodiment and a First Modified Embodiment described above will bedenoted by the same reference signs, and descriptions thereof will beomitted.

Although not illustrated, in the substrate processing apparatus of theSecond Modified Embodiment, a solid is disposed on an inner surface of aceiling 74 of an inner tube 4B facing a boat top plate 21B. The solidincludes a porous or sintered body to which one species of a product gas(e.g., SiCl₂ as a silylene) is adsorbed, and the product gas is consumedto decrease a partial pressure of the product gas to a degree equivalentto a product wafer having a pattern formed. As the solid, for example, aplate material having a surface with regularities and machined in ascale larger than a scale of a pattern of a product wafer is used, andthe solid has large surface area capable of performing adsorption by themachined surface and pores (micropores) of the solid material itself. Inthe pores, unique phenomena such as Knudsen diffusion or capillarycondensation dependent on a gas molecular weight occurs, and therefore,at least some of the pores each have an inner diameter selected within arange of 10 to 100 nm, for example, conforming to a pattern of a wafer.Furthermore, in a case where distribution of diameters of the pores ismade constant in the range from several tens of nanometers to severalhundreds of nanometers, the solid can be used for a relatively longperiod without replacement even when a pore is blocked due todeposition. In the Second Modified Embodiment, for example, a pluralityof plate materials each having the surface with regularities is arrangedalong, for example, the inner surface of the ceiling 74 in a spacebetween the ceiling 74 and the boat top plate 21B, namely, a soakingregion. An arrangement interval may be narrow and, for example, and canbe selected within a range of 2 to 3 mm.

The substantial surface area of the solid is, for example, 0.1 times ormore and 1.0 times or less surface area of a front side of a productwafer. The substantial surface area of the solid is preferably 0.1 timesor more and 1.0 time or less, more preferably 0.2 times or more and 0.7times or less, and still more preferably 0.3 times or more and 0.6 timesor less the surface area of the front side of the product wafer. Asource gas is not actively supplied to an upper end space between theboat top plate 21B and the ceiling 74 of the inner tube 4B, and thesource gas flows from a clearance between the boat top plate 21B and theinner surface of the inner tube 4B. Therefore, the substantial surfacearea of the solid may be 1.0 time or less the surface area of the frontside of the product wafer. Since the substantial surface area of thesolid is set to 0.1 times or more the surface area of the front side ofthe product wafer, the product gas (e.g., SiCl₂) can be more effectivelyadsorbed and consumed in the upper end space.

Consequently, it is possible to reduce a concentration difference of onespecies of product gas (e.g., SiCl₂) between the space inside theceiling 74 of the inner tube 4B and the product wafer. Therefore, whenthe product wafers are held at all of positions in a boat 21 where thewafers 7 can be held, thicknesses of films formed on the wafers 7 can bemore effectively prevented from being non-uniform among the wafers 7.

Meanwhile, instead of providing the solid on the inner surface of theceiling 74 of the inner tube 4B facing the boat top plate 21B, a surface(quartz surface) on an inner side of the ceiling 74 of the inner tube 4Bmay be machined to have irregularities.

According to this present disclosure, thicknesses of films respectivelyformed on a plurality of substrates arrayed in the vertical direction ofthe substrate holder can be prevented from being non-uniform among thesubstrates.

While this present disclosure has been described in detail with respectto the specific embodiments, this present disclosure is not limited tothe embodiments, and it is obvious to a person skilled in the art thatvarious other embodiments can be made within the scope of this presentdisclosure.

What is claimed is:
 1. A substrate processing apparatus comprising: asubstrate holder configured to hold plurality of substrates in array atrespective positions with predetermined intervals and used to hold aplurality of product substrates at all the positions where thesubstrates are allocable; a tubular reactor including an opening throughwhich the substrate holder can be carried in and out at a lower side anda ceiling with a flat inner surface and houses the substrate holder; afurnace body surrounding an upper side and a lateral side of the tubularreactor; a main heater provided in the furnace body and configured toheat the side portion of the tubular reactor; a ceiling heater providedin the furnace body and configured to heat the ceiling; a lid thatcloses the opening; a cap heater arranged inside the tubular reactor andalso located below the substrate holder and configured to performheating; and a gas supply mechanism configured to individually supply agas to a top side of each of the plurality of product substrates held bythe substrate holder inside the tubular reactor, wherein when a sourcegas decomposable in a gas phase is supplied from the gas supplymechanism in a state where the product substrates are held at all of thepositions in the substrate holder, a partial pressure of a species of aproduct gas generated by the decomposition becomes uniform at all of thepositions; wherein the substrate holder includes a plurality ofupstanding support columns and a disk-shaped top plate that fixes upperends of the plurality of support columns; wherein a diameter of the topplate is set to 90% or more and 98% or less of an inner diameter of thetubular reactor substrate; and wherein volume of an upper end spacepartitioned from others by the top plate and interposed between theceiling and the top plate is set to 1 time or more and 3 times or lessvolume of a space interposed between the product substrates adjacent toeach other and held by the substrate holder.
 2. The substrate processingapparatus according to claim 1, wherein the substrate holder includes aplurality of upstanding support columns and a disk-shaped top plate thatfixes upper ends of the plurality of support columns; wherein a diameterof the top plate is set to 90% or more and 98% or less of an innerdiameter of the tubular reactor and a pitch between the adjacent productsubstrates held by the substrate holder is set to 6 mm or more and 16 mmor less; and wherein volume of an upper end space partitioned fromothers by the top plate and interposed between the ceiling and the topplate is set to 1 time or more and 3 times or less volume of a spaceinterposed between the product substrates adjacent to each other andheld by the substrate holder.
 3. The substrate processing apparatusaccording to claim 2, wherein: the substrate holder further includes adisk-shaped or annular bottom plate that fixes lower ends of theplurality of support columns to each other and is fitted to an uppersurface of the insulation structure; volume of a lower end spaceinterposed between the bottom plate or the upper surface of the heatinsulation structure and the product substrate held at a lowermostposition in the substrate holder where the substrate can be held is setto 0.5 times or more and 1.5 times or less volume of a space interposedbetween the product substrates adjacent to each other and held by thesubstrate holder; and the gas supply mechanism individually supplies thesource gas to the lower end space.
 4. The substrate processing apparatusaccording to claim 1, wherein the gas supply mechanism comprises anozzle that is located beside the array of the plurality of substrates,fed the gas flow-controlled from a single pipe, distributes the gas intonozzle holes and discharges the gas through the nozzle holes towardspaces above or edges of all the plurality of product substrates held bythe substrate holder inside the tubular reactor.
 5. A method ofmanufacturing a semiconductor device, using the substrate processingapparatus according to claim 1, the method sequentially repeating: afirst process in which a gas supply mechanism supplies a first sourcegas to a plurality of product substrates; a second process in which thegas supply mechanism supplies a purge gas to the plurality of productsubstrates; a third process in which the gas supply mechanism supplies asecond source gas to the plurality of product substrates; and a fourthprocess in which the gas supply mechanism supplies a purge gas to theplurality of product substrates.
 6. A substrate processing apparatuscomprising: a substrate holder configured to hold plurality ofsubstrates in array at respective positions with predetermined intervalsand used to hold a plurality of product substrates at all the positionswhere the substrates are allocable; a tubular reactor including anopening through which the substrate holder can be carried in and out ata lower side and a ceiling with a flat inner surface and houses thesubstrate holder; a furnace body surrounding an upper side and a lateralside of the tubular reactor; a main heater provided in the furnace bodyand configured to heat the side portion of the tubular reactor; aceiling heater provided in the furnace body and configured to heat theceiling; a lid that closes the opening; a cap heater arranged inside thetubular reactor and also located below the substrate holder andconfigured to perform heating; and a gas supply mechanism configured toindividually supply a gas to a top side of each of the plurality ofproduct substrates held by the substrate holder inside the tubularreactor, wherein when a source gas decomposable in a gas phase issupplied from the gas supply mechanism in a state where the productsubstrates are held at all of the positions in the substrate holder, apartial pressure of a species of a product gas generated by thedecomposition becomes uniform at all of the positions; wherein thesubstrate holder further includes a disk-shaped or annular bottom platethat fixes lower ends of the plurality of support columns to each otherand is fitted to an upper surface of the insulation structure; volume ofa lower end space interposed between the bottom plate or the uppersurface of the heat insulation structure and the product substrate heldat a lowermost position in the substrate holder where the substrate canbe held is set to 0.5 times or more and 1.5 times or less volume of aspace interposed between the product substrates adjacent to each otherand held by the substrate holder; and the gas supply mechanismindividually supplies the source gas to the lower end space.
 7. Thesubstrate processing apparatus according to claim 6, wherein the openingof the main exhaust vent further faces the lower end space.